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[Gradescender]

Hi, all. I've read a few different things and I'm a bit unsure of what actually happens to the stretched muscle in LL. I've heard that if it is overstretched, it looses its elasticity and your power/force production is never the same (I believe Dr. Donghoon Lee has the rubber band analogy). I've also read that the muscle responds to overstretch by generating new tissue, or sarcomere units.

Stretching Skeletal Muscle: Chronic Muscle Lengthening through Sarcomerogenesis
https://www.researchgate.net/publication/232226780_Stretching_Skeletal_Muscle_Chronic_Muscle_Lengthening_through_Sarcomerogenesis

Does some combination of both happen in real-world procedures? Do the 18%-20% lengthening limits keep things under some threshold where muscle ceases to be able to undergo sufficient sarcomerogenesis so that the muscle can settle into its new "operating regime"? Do some people develop soft tissue problems as a result of some mismatch of distraction rate and their individual physiology? (ex: maybe their bone consolidation is occurring too quickly, so faster distraction rate and their muscle cannot enough lay down enough new sarcomere units to keep up with the tension). Is the procedure some kind of balancing act between these things? Just trying to understand the interplay between stretching existing muscle, the formation of new muscle, and tightness/weakness in some patients after lengthening. Hopefully this question makes sense and thank you for letting me pick your brains on this. 

I am a very active person as an adult (30s), but my posterior chain is a bit shortened due to heels/lifts and no stretching or working out throughout high school and college. I've been working on these issues pretty diligently with a PT but uncertain how much more progress I can make, so pretty concerned about changes in tissue quality.

[cyborg4life]

I think this is super interesting. I agree with this and other research I've found on this topic. More studies should definitely look into this

[KiloKAHN]

There appears to be both stretching and sarcomerogenesis, but the stretching can only go so far. My surgeon kind of addressed this when he was asked why his max for tibial lengthening is 6 cm.

Dr Parihar: The general experience, and my own experience has been that after 5 cms, people start having trouble with more pain, difficulty to exercise their muscles, and start developing deformities such as equinus (ballerina) and flexion of the knee. Muscles can stretch to a point (like a rubber band), but beyond that point they lose their elasticity (and become like a rope). Initially muscle stretch keeps pace with the increase in length of the bone, beyond 5 cms the muscles are not stretching enough to keep pace with the bone lengthening. They then pull on whatever bone/joint they are attached to and cause deformities which are very difficult to stretch out with physio, and require surgery.

http://www.limblengtheningforum.com/index.php?topic=2783.msg43784#msg43784

[ReadRothbard]

The tissue itself actuallu grows--it's not just the stretching of muscular tissue.

[Gradescender]

There appears to be both stretching and sarcomerogenesis, but the stretching can only go so far. My surgeon kind of addressed this when he was asked why his max for tibial lengthening is 6 cm.

Dr Parihar: The general experience, and my own experience has been that after 5 cms, people start having trouble with more pain, difficulty to exercise their muscles, and start developing deformities such as equinus (ballerina) and flexion of the knee. Muscles can stretch to a point (like a rubber band), but beyond that point they lose their elasticity (and become like a rope). Initially muscle stretch keeps pace with the increase in length of the bone, beyond 5 cms the muscles are not stretching enough to keep pace with the bone lengthening. They then pull on whatever bone/joint they are attached to and cause deformities which are very difficult to stretch out with physio, and require surgery.

http://www.limblengtheningforum.com/index.php?topic=2783.msg43784#msg43784

Thanks. I guess it was here that I read the rubber band analogy and it was Dr. Parihar, not Dr. Lee. Parihar mentions muscle stretch in the interview but not the production of new tissue really. I would like to know when tissue formation happens and what conditions may interfere with that.
Does new tissue form as you are stimulating it with passive overstretch during lengthening, or does it mostly form after the lengthening phase under full stretch?
If it's more the latter, that explains why he is only discussing muscle stretching and respecting the limits of that. Things could be too wonky or inflamed after 5cm for new tissue to form properly. If it's more the former (new tissue forms gradually as you lengthen), how well you end up optimizing for new muscle growth instead of lengthened/inelastic muscle seems like it could be a crapshoot for each patient.

The quote also makes it sounds like the 5cm marker is based mostly on collective experience, but I was hoping there was a more detailed, mechanism-level explanation as well. 

I think this is super interesting. I agree with this and other research I've found on this topic. More studies should definitely look into this

Hi cyborg. Thanks for your content. I see you have a thread on questions for the surgeons. Could there be a question in the future on the timing and the limits of new muscle formation as you are doing LL? Is sarcomerogenesis deliberately optimized for at all in LL protocols and if so, how?
I agree, super interesting topic.

[MakeMeTallAF]

In cyborgs interviews with paley and rozbruch they mention soft tissues undergo histeogenesis during distraction, meaning there is new tissue formation as they are stretched.

The process is called distraction histeogenesis. This is also why your skin grows as your leg grows, and likely the muscles grow too.